Methods and Systems for Applying Charge to a Piezoelectric Element

ABSTRACT

Methods and systems for applying charge to a piezoelectric element include and/or facilitate implementation of processes including cyclical multi-stage processes for: providing a piezoelectric element with an accumulated charge; providing one or more charge holding elements with a scavenged charge from the piezoelectric element; substantially removing or discharging a remaining charge from the piezoelectric element; and applying the scavenged charge to the piezoelectric element with an opposite polarity in relation to the polarity of the remaining charge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/748,569, filed on Jan. 23, 2013, which claims the benefit of U.S.Provisional Application No. 61/589,736, filed on Jan. 23, 2012, both ofwhich are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to piezoelectric devices and, inparticular, methods and systems for applying charge to and recoveringcharge from a piezoelectric element or device.

BACKGROUND ART

A piezoelectric element is a crystalline material which produces anelectric voltage when subjected to mechanical pressure. In view of theirvarious properties, piezoelectric elements have been used as actuatorsin diaphragm displacement pumps. In general, piezoelectric actuators ofthe type used in pumps require excitation by a regularly reversinghigh-voltage field. Depending on the application, the excitation voltagemay be anywhere from 25 to 1000 volts or more and the frequency of fieldreversal may be anywhere from a fraction of a cycle per second tothousands of cycles per second. Typically, this excitation signal mustbe derived from a relatively low-voltage source of 1.5-25 volts. Seee.g., U.S. Pat. No. 7,287,965 B2, which is hereby incorporated byreference.

It would be useful to be able to provide methods and systems forapplying charge to piezoelectric elements/devices that are more energyefficient. It would be useful to be able to improve energy utilizationby a piezoelectric pump or device.

SUMMARY OF THE INVENTION

In an example embodiment, a method for applying charge to apiezoelectric element includes: imparting a scavenged charge to one ormore charge holding elements, said scavenged charge being at least aportion of an accumulated charge associated with a piezoelectricelement; and coupling a voltage source or reference and the one or morecharge holding elements to the piezoelectric element such that aremaining charge on the piezoelectric element is removed and thescavenged charge is applied to the piezoelectric element with anopposite polarity in relation to the polarity of the remaining charge.

In an example embodiment, a method for applying charge to apiezoelectric element includes: providing a piezoelectric element withan accumulated charge; providing one or more charge holding elementswith a scavenged charge from the piezoelectric element; substantiallyremoving or discharging a remaining charge from the piezoelectricelement; and applying the scavenged charge to the piezoelectric elementwith an opposite polarity in relation to the polarity of the remainingcharge.

In an example embodiment, a system including electronics for producing adrive signal for a device having a piezoelectric transducer includes: acontroller configured to generate voltage pulses; and convertercircuitry including one or more charge holding elements, the convertercircuitry being configured to use the voltage pulses to develop anaccumulated charge associated with the piezoelectric transducer, providethe one or more charge holding elements with a scavenged charge from thepiezoelectric transducer, substantially remove or discharge a remainingcharge from the piezoelectric transducer, and apply the scavenged chargeto the piezoelectric transducer with an opposite polarity in relation tothe polarity of the remaining charge.

In an example embodiment, a pump includes: a pump body configured to atleast partially define a pumping chamber; a piezoelectric elementresponsive to a drive signal for pumping fluid in the pumping chamber;and a pump driver configured to provide the drive signal, the pumpdriver including a flyback boost circuit configured to develop anaccumulated charge associated with the piezoelectric element and also acharge on one or more charge holding elements, a charge scavengingcircuit configured to provide a charge scavenged from the piezoelectricelement to the one or more charge holding elements, a charge removingcircuit configured to substantially remove or discharge a remainingcharge from the piezoelectric element, and a charge reclaiming circuitconfigured to apply the scavenged charge to the piezoelectric elementwith an opposite polarity in relation to the polarity of the remainingcharge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a pump including a piezoelectric element;

FIG. 2 is a diagram of a system including a drive circuit/electronicsfor producing a drive signal for a piezoelectric element or device;

FIG. 3 is a flow diagram of an example method for applying charge to apiezoelectric element;

FIG. 4 is an electrical schematic showing an example embodiment of apiezoelectric driver circuit;

FIG. 5 is a plot showing voltage and control input levels during anexample operation cycle implemented by the piezoelectric driver circuitof FIG. 4;

FIG. 6 shows a typical bipolar signal generated by the present inventionfor driving the piezoelectric element; and

FIGS. 7-12 show a piezoelectric driver circuit at different stagesrespectively during an example implementation of a multi-stage process.

DISCLOSURE OF INVENTION

The methodologies and technologies described herein generally involveapplying charge to a piezoelectric element and can include (and/orfacilitate implementation of processes including cyclical multi-stageprocesses for) one or more of, for example: providing a piezoelectricelement with an accumulated charge; providing one or more charge holdingelements with a scavenged charge from the piezoelectric element;substantially removing or discharging a remaining charge from thepiezoelectric element; and applying the scavenged charge to thepiezoelectric element with an opposite polarity in relation to thepolarity of the remaining charge.

Referring to FIG. 1, a pump 100 includes a pump body 102 (e.g.,configured to at least partially define a pumping chamber) and a drivecircuit 104. Referring to FIG. 2, in an example embodiment, a system 200includes drive circuit/electronics 204 for producing a drive signal fora piezoelectric element or device, a controller 210 (e.g., implementedutilizing one or more microcontrollers), a converter circuit andpiezoelectric element/device 220, and a power source 230 configured asshown.

Referring to FIG. 3, in an example embodiment, a method 300 for applyingcharge to a piezoelectric element (or piezoelectric load) includes, atstep 302, providing a piezoelectric element with an accumulated charge(e.g., utilizing pulses to provide a piezoelectric element with anaccumulated charge and also a charge on one or more charge holdingelements, such as a capacitor or a second piezoelectric element). Forexample, the accumulated charge is developed from (voltage) pulses(e.g., unipolar DC voltage pulses) provided by a voltage source (e.g., aDC voltage source or power supply, a fixed or regulated voltage orpotential). At step 304, one or more charge holding elements areprovided with a scavenged charge (scavenged or otherwise obtained) fromthe piezoelectric element. At step 306, a remaining charge (held by thepiezoelectric element) is substantially removed or discharged from thepiezoelectric element. For example, substantially removing ordischarging a remaining charge includes coupling a voltage source to aterminal (e.g., the positive terminal) of the piezoelectric element. Atstep 308, the scavenged charge (held by the one or more charge holdingelements) is applied to the piezoelectric element (e.g., with anopposite polarity in relation to the polarity of the remaining chargepreviously held by the piezoelectric element). For example, applying thescavenged charge includes decoupling (e.g., disconnecting) a terminal ofthe piezoelectric element (e.g., the negative terminal) from anelectrical ground, and coupling the one or more charge holding elementsto (said terminal of) the piezoelectric element.

Referring to FIG. 4, in this example embodiment, a piezoelectric drivercircuit 400 includes a flyback boost circuit 402 (Q1, T1, T2, D1, D2)configured to develop an accumulated charge (on or) associated with thepiezoelectric element and also a charge on one or more charge holdingelements (e.g., the flyback boost circuit including an inductor arrayconfigured such that different portions of the array are utilized fortransferring charge to the piezoelectric element and C1, respectively).The capacitive element C1 can be provided, by way of example and not oflimitation, as a discrete capacitor, a configuration of multiple(selectable) capacitive components, simulated capacitance(s), or acombination thereof. In example embodiments (involving a dual channelpump, for example), the one or more charge holding elements include asecond piezoelectric element or transducer. The piezoelectric drivercircuit 400 further includes a charge scavenging circuit 404 (S1—suchas, for example, silicon-controlled rectifier S602TS) (e.g., connectedbetween the piezoelectric element and the one or more charge holdingelements) configured to provide a charge scavenged (or otherwiseobtained) from the piezoelectric element to the one or more chargeholding elements (e.g., C1 or a second piezoelectric element ortransducer). In this example embodiment, the piezoelectric drivercircuit 400 includes a charge removing circuit 406 (Q2—such as, forexample, 100V plus N-channel MOSFET ZVN0545) (e.g., connected to thepositive terminal of the piezoelectric element) configured tosubstantially remove or discharge a remaining charge from thepiezoelectric element, and a charge reclaiming circuit 408 (Q3, S2—suchas, for example, power MOSFET IRFR4615 and silicon-controlled rectifierS602TS, respectively) (e.g., connected to the piezoelectric element andthe one or more charge holding elements) configured to apply thescavenged charge (held by the one or more charge holding elements) tothe piezoelectric element (e.g., with an opposite polarity in relationto the polarity of the remaining charge previously held by thepiezoelectric element).

In an example implementation, the piezoelectric driver circuit 400 isconfigured to drive a piezoelectric drug pump (e.g., to drive thepiezoelectric element to +285 volts and then reverse polarity and drivethe element to −75 volts), and the power supply is +3 volts.

The flyback boost converter 400 is formed with transistor Q1 (such as,for example, power MOSFET IRFR4615), coils T1 and T2 (such as, forexample, dual winding inductors DRQ73-221) and diodes D1 and D2 (suchas, for example, rectifier diodes MURS-160). Further switching andauxiliary capacitor, C1, are utilized to facilitate the scavenging ofenergy (from the piezoelectric element) and reversal of polarity at thepiezo.

In an example implementation, coils T1 and T2 have two identicalwindings each, and a single coil exhibits 220 microhenries ofinductance. In this circuit one winding from each coil is placed inparallel with a winding from the other coil. This parallel pair isdriven by Q1 to store energy. The remaining two windings of the twocoils are connected in series and attached to the paralleled pair sothat the whole inductive array will exhibit three times the voltage seenacross the paralleled pair. Referring additionally to FIGS. 5 and 6,when Q1 is pulsed by drive line A it applies the 3 volt supply acrossthe paralleled pair of windings and current ramps up to 0.5 Amps. Whenline A drops Q1 turns off and the flyback effect forces current throughdiodes D1 and D2 to charge the piezo element and C1 simultaneously. Thecurrent through the coils provides the charge that is transferred to thepiezo and C1. The high voltage flyback circuit provides the voltagesufficient to cause the charge transfer. While D1 is driven by the wholeinductor array, D2 is only driven by the paralleled windings. As aconsequence, and referring to FIG. 6 which shows a bipolar signal 600transitioning from a positive signal 602 to a negative signal 604, after9 pulses the piezo will have reached 285 volts and C1 will only havereached 95 volts. During this time transistor Q2 will be off and Q3 willbe on to allow current through the piezo access to ground. Once thepiezo and the C1 are charged SCR S1 will be triggered by line E andcharge from the piezo will be transferred to C1 raising it to +190volts. Next Q2 is turned on to remove the remaining charge from thepiezo. Q2 is connected to the +3 volt supply, otherwise supply currentwould flow through the coils, D1 and Q2 to ground. The next step is toturn Q3 off and trigger S2 using a pulse from line D. This will transfercharge from C1 to the opposite electrode of the piezo from the one whichhad previously held a positive charge. The resulting voltage should be+78 volts to produce a differential across the piezo of −75 voltsreferenced to the original charge of +285 volts. Finally transistor Q3will be turned on to discharge the remaining charge on the piezo. Q2will be turned off and the system will be ready for the next cycle.Thus, in an example embodiment, a pump includes a pump body configuredto at least partially define a pumping chamber, a piezoelectric element(e.g., a piezoelectric transducer or actuator situated in the pump bodyor external to the body) responsive to a drive signal for pumping fluidin the pumping chamber, and a pump driver configured to provide thedrive signal (responsive to voltage pulses generated, for example, by amicrocontroller). The pump driver includes a flyback boost circuit (Q1,T1, T2, D1, D2) configured to develop an accumulated charge (on or)associated with the piezoelectric element and also a charge on one ormore charge holding elements (e.g., the flyback boost circuit includingan inductor array configured such that different portions of the arrayare utilized for transferring charge to the piezoelectric element andC1, respectively), a charge scavenging circuit (S1) (e.g., connectedbetween the piezoelectric element and the one or more charge holdingelements) configured to provide a charge scavenged (or otherwiseobtained) from the piezoelectric element to the one or more chargeholding elements (e.g., C1), a charge removing circuit (Q2) (e.g.,connected to the positive terminal of the piezoelectric element)configured to substantially remove or discharge a remaining charge fromthe piezoelectric element, and a charge reclaiming circuit (Q3, S2)(e.g., connected to the piezoelectric element and the one or more chargeholding elements) configured to apply the scavenged charge (held by theone or more charge holding elements) to the piezoelectric element (e.g.,with an opposite polarity in relation to the polarity of the remainingcharge previously held by the piezoelectric element).

The pump driver is configured, for example, to provide the drive signalresponsive to voltage pulses (e.g., unipolar DC voltage pulses). Inexample embodiments, the pump includes a controller (e.g.,microcontroller) configured to generate the voltage pulses. The one ormore charge holding elements include, for example, a capacitor or asecond piezoelectric element. The flyback boost circuit includes, forexample, an inductor array configured such that different portions ofthe array (or combinations thereof) are utilized for transferring chargeto the piezoelectric element and a capacitor (e.g., C1), respectively.The flyback boost circuit includes, for example, an inductor arrayconfigured such that different portions of the array (or combinationsthereof) are utilized for transferring charge to first and secondpiezoelectric elements, respectively. In example embodiments, the pumpdriver is configured to apply the scavenged charge to the piezoelectricelement with an opposite polarity in relation to the polarity of theremaining charge (previously held by the piezoelectric element). Inexample embodiments, the pump driver is configured such thatcapacitances of the piezoelectric element and the one or more chargeholding elements (e.g., C1) determine how much charge is reclaimed(e.g., both at 2 nF; more charge reclaimed if C1 is increased to, say,20 nF while the capacitance of the piezoelectric element remains 2 nF).In example embodiments, the capacitance of a capacitor (e.g., C1) is atleast as large as the capacitance of the piezoelectric element.

In example embodiments, the converter circuitry is configured toimplement a multi-stage (e.g., two-stage) process utilizing the one ormore charge holding elements (for example, different elements of acapacitive bank are utilized for different stages or portions of amulti-stage process).

FIGS. 7-12 show a piezoelectric driver circuit at different stagesrespectively during an example multi-stage process implemented as setforth below:

Pre/Post Fire

-   The Pre/Post Fire State is the idle state of the circuit. This is    the circuit configuration that is used in between pump stroke    events.    -   Stage 1-   During Stage 1, switch A is closed, connecting the power supply to    ground through the inductance L1. The current will develop to a    desired level at which time the circuit moves to Stage 2.

Stage 2

-   When switch A is opened, the physics of the circuit creates a very    high voltage at L1. This high voltage causes current to flow through    L2/D2 and onto the piezo PZ as well as through D1 onto the capacitor    CAP.

Cycle Stage 1 and Stage 2

-   Each time the circuit is cycled through Stage 1 and Stage 2, more    and more charge accumulates on the piezo PZ and the capacitor. Once    the desired voltage has been accumulated on the piezo PZ, the    circuit moves to Stage 3.

Stage 3

-   The charge on the piezo PZ is available for scavenging in order to    make the circuit more efficient. On Stage 3, the positive terminal    of the piezo is connected to the positive terminal of the capacitor    by closing switch E. Since the piezo is charged to a much higher    voltage than the capacitor, charge will flow from the piezo to the    capacitor until the charge on each component is equalized in    proportion to their respective capacitances.

Stage 4

-   During Stage 4 the remaining charge on the positive terminal of the    piezo is removed by closing switch B and thus connecting the    positive terminal of the pieze to the positive supply. Note that the    positive terminal of the piezo is not connected to ground in this    circuit topology because doing so would create a path from the    positive supply to ground through L1/L2/D2, wasting battery current.    By connecting the piezo to the supply voltage instead, enough of the    charge will be removed to make the circuit work, however the    positive terminal of the piezo will not be at zero volts but rather    at the supply voltage. Other or alternative circuit implementations    (e.g., connecting the piezo to a different voltage or reference) can    also be utilized.

Stage 5

-   In order to reverse the polarity on the piezo from the high positive    voltage originally developed in Stage 2, the charge that was    scavenged in Stage 3 is now applied to the opposite terminal of the    piezo. Note that switch C is opened to disconnect the piezo terminal    from ground and the terminal is connected to the capacitor by    closing switch D. The piezo will be charged now in an opposite    polarity from Stage 2 to a somewhat lesser voltage.

Stage 6

-   Return to the Pre/Post Fire stage.

Thus, in an example embodiment, a system including electronics forproducing a drive signal (e.g., piezo driver) for a device (e.g., a drugpump) having (or operatively connected to) a piezoelectric transducer(e.g., a piezoelectric actuator forming a part of the electronics andserving to shape a waveform of the drive signal). The electronicsinclude a controller (e.g., microcontroller) configured to generatevoltage pulses and converter circuitry including one or more chargeholding elements (e.g., C1). The converter circuitry is configured touse the voltage pulses to develop an accumulated charge (on or)associated with the piezoelectric transducer (and also a charge on oneor more charge holding elements), provide the one or more charge holdingelements (e.g., C1) with a scavenged charge (scavenged or otherwiseobtained) from the piezoelectric transducer, substantially remove ordischarge a remaining charge from the piezoelectric transducer, andapply the scavenged charge (held by the one or more charge holdingelements) to the piezoelectric transducer (e.g., with an oppositepolarity in relation to the polarity of the remaining charge previouslyheld by the piezoelectric transducer).

In example embodiments, the controller is configured to operate withoutsensed or other feedback from the converter circuitry or thepiezoelectric transducer. The converter circuitry can include abuck-boost circuit configured to accumulate charge developed from thevoltage pulses (e.g., unipolar DC voltage pulses) via flyback, and theone or more charge holding elements can include a capacitor (e.g., C1)or a second piezoelectric transducer connected (or electrically coupled)to the buck-boost circuit.

In example embodiments, the converter circuitry is configured to developthe accumulated charge from (unipolar) DC voltage pulses (e.g., viaflyback).

In example embodiments, the converter circuitry is configured to couplea voltage source (e.g., 3 VDC) to the piezoelectric transducer (and theone or more charge holding elements).

In example embodiments, the converter circuitry includes inductiveelements (e.g., two or more of which are connect in series between thevoltage source and the piezoelectric transducer). The inductive elementscan be utilized to govern pulse width (of the voltage pulses). Inexample implementations, the inductive elements include matchedinductive elements and/or are non-magnetic. In example implementations,the inductive elements include a paralleled pair and a series pair ofinductive elements (e.g., configured in series with a diode (e.g., DObetween the voltage source and the positive terminal of thepiezoelectric transducer.

With reference to FIGS. 7-12, the converter circuitry includes inductiveelements (L1 and L2) connected in a series-aiding (boosting)configuration. The converter circuitry can include a first diode (D1)connected to the piezoelectric transducer and a second diode (D2)connected to the capacitor or a second piezoelectric transducer.

In example embodiments, the converter circuitry includes a chargescavenging circuit (S1) connected between the piezoelectric transducerand the one or more charge holding elements (e.g., configured to providecharge from the piezoelectric transducer to the one or more chargeholding elements). In example embodiments, the converter circuitryincludes a charge removing circuit (Q2) connected to the (positiveterminal of the) piezoelectric transducer (e.g., configured tosubstantially remove or discharge a remaining charge from thepiezoelectric transducer). In example embodiments, the convertercircuitry includes a charge reclaiming circuit (Q3, S2) connected to thepiezoelectric transducer and the one or more charge holding elements andconfigured to apply the scavenged charge to the piezoelectric transducer(e.g., with an opposite polarity in relation to the polarity of theremaining charge previously held by the piezoelectric transducer). Inexample embodiments, the converter circuitry is configured such thatcapacitances of the piezoelectric transducer and the one or more chargeholding elements (e.g., C1) determine how much charge is reclaimed(e.g., both at 2 nF; more charge reclaimed if C1 is increased to, say,20 nF while the capacitance of the piezoelectric transducer remains 2nF). In example embodiments, the capacitance of a capacitor (e.g., C1)is at least as large as the capacitance of the piezoelectric transducer.In example embodiments, the converter circuitry is configured toimplement a multi-stage (e.g., two-stage) process utilizing the one ormore charge holding elements (for example, different elements of acapacitive bank are utilized for different stages or portions of amulti-stage process).

Thus, in an example embodiment, a method for applying charge to apiezoelectric element (or piezoelectric load) includes: imparting ascavenged charge to one or more charge holding elements (i.e., elementscapable of holding an electric charge, such as a capacitive element),said scavenged charge being at least a portion of a charge (e.g., anaccumulated charge) (on or) associated with a piezoelectric element (orpiezoelectric load), and coupling a voltage source or reference (e.g., aDC voltage source or power supply, a voltage reference or level,fixed/regulated potential, or circuit ground) and the one or more chargeholding elements to the piezoelectric element such that a (remaining)charge on the piezoelectric element is removed (or discharged) (orsubstantially removed/discharged) and the scavenged charge (held by theone or more charge holding elements) is applied to the piezoelectricelement with an opposite polarity in relation to the polarity of theremaining charge (previously held by the piezoelectric element). The oneor more charge holding elements include, for example, a capacitor or asecond piezoelectric element.

In example embodiments, the method further includes utilizing a sequenceof pulses to provide the accumulated charge (and also a charge on theone or more charge holding elements). In example embodiments, the methodfurther includes utilizing additive electromotive forces to provide theaccumulated charge (and also a charge on the one or more charge holdingelements).

In example embodiments, the method further includes utilizing pulses(e.g., a sequence of pulses) to provide the accumulated charge and alsoa charge on the one or more charge holding elements. In exampleembodiments, the method further includes utilizing additiveelectromotive forces to provide the accumulated charge and also a chargeon the one or more charge holding elements.

The accumulated charge is developed, for example, from voltage pulses(e.g., unipolar DC voltage pulses) via flyback. In example embodiments,the method further includes developing the accumulated charge from(unipolar) DC voltage pulses (e.g., via flyback). For example,developing the accumulated charge includes coupling (e.g., inductivelycoupling) the voltage source to the piezoelectric element (and the oneor more charge holding elements).

In example embodiments, the method further includes utilizing aninductive coupling to provide the charge (and also a charge on the oneor more charge holding elements). In example embodiments, coupling avoltage source (or reference voltage) (or circuit ground) and the one ormore charge holding elements to the piezoelectric element includes oneor more of, for example: providing charge from the piezoelectric elementto the one or more charge holding elements, equalizing charge as betweenthe piezoelectric element and the one or more charge holding elements(e.g., in proportion to their respective capacitances), coupling thevoltage source to a terminal (e.g., the positive terminal) of thepiezoelectric element to remove or dissipate charge accumulated orremaining on the piezoelectric element, and decoupling (e.g.,disconnecting) a terminal of the piezoelectric element (e.g., thenegative terminal) from an electrical ground, and coupling the one ormore charge holding elements to (said terminal of) the piezoelectricelement to apply the scavenged charge to the piezoelectric element.

Example implementations of the methodologies and technologies hereininvolve various design requirements and assumptions, theories ofoperation, and testing and implementation particulars, such as, forexample:

Design Requirements

-   -   Bipolar High Voltage Flyback Circuit capable of +285 V and −75V    -   Pump drive circuit capable of achieving 2 mJ/μL energy        efficiency or better

Design Assumptions:

-   -   Positive voltage (+285V) precedes negative voltage (−75V)    -   Voltage supply is a stable 3V    -   Flyback clock sources derived from the CPU    -   10V Supply required to drive the FETs    -   Piezo Pump Load approximately 2 nF for benchtop emulation

Theory of Operation (FIGS. 4 and 5)

-   -   Stage 1: A flyback circuit driven by a clock makes/breaks an        inductive circuit to generate high voltage pulses. The high        voltage accumulates via a diode onto a storage capacitor until        +285V is reached.    -   Stage 2: The +285V is applied to the piezo load. When the pulse        is over, the charge is scavenged back to another storage        capacitor resulting in a +70V charge.    -   Stage 3: A −70V pulse is applied to the piezo pump from the        scavenged charge capacitor by applying it in inverse polarity.

Conclusion

-   -   The battery life curve is an important consideration to the        design.    -   CPU control of flyback clocks and drive signals can determine        pulse timing.

Although the present invention(s) has(have) been described in terms ofthe example embodiments above, numerous modifications and/or additionsto the above-described embodiments would be readily apparent to oneskilled in the art. It is intended that the scope of the presentinvention(s) extend to all such modifications and/or additions.

1-19. (canceled)
 20. A system including electronics for producing adrive signal for a device having a piezoelectric transducer, theelectronics comprising: a controller configured to generate voltagepulses; and converter circuitry including one or more charge holdingelements, the converter circuitry being configured to use the voltagepulses to develop an accumulated charge associated with thepiezoelectric transducer, provide the one or more charge holdingelements with a scavenged charge from the piezoelectric transducer,substantially remove or discharge a remaining charge from thepiezoelectric transducer, and apply the scavenged charge to thepiezoelectric transducer with an opposite polarity in relation to thepolarity of the remaining charge.
 21. The system of claim 20, whereinthe controller is configured to operate without sensed or other feedbackfrom the converter circuitry or the piezoelectric transducer.
 22. Thesystem of claim 20, wherein the converter circuitry includes abuck-boost circuit configured to accumulate charge developed from thevoltage pulses via the flyback effect.
 23. The system of claim 22,wherein the one or more charge holding elements include a capacitor or asecond piezoelectric transducer connected to the buck-boost circuit. 24.The system of claim 20, wherein the converter circuitry is configured todevelop the accumulated charge from DC voltage pulses.
 25. The system ofclaim 20, wherein the converter circuitry is configured to couple avoltage source to the piezoelectric transducer.
 26. The system of claim20, wherein the converter circuitry includes inductive elements.
 27. Thesystem of claim 26, wherein the inductive elements govern pulse width.28. The system of claim 26, wherein the inductive elements are notmagnetically coupled.
 29. The system of claim 20, wherein the convertercircuitry includes inductive elements connected in a series-aidingboosting configuration.
 30. The system of claim 20, wherein the one ormore charge holding elements include a capacitor or a secondpiezoelectric transducer.
 31. The system of claim 30, wherein theconverter circuitry includes a first diode connected to thepiezoelectric transducer and a second diode connected to the capacitoror the second piezoelectric transducer.
 32. The system of claim 20,wherein the converter circuitry includes a charge scavenging circuitconnected between the piezoelectric transducer and the one or morecharge holding elements.
 33. The system of claim 20, wherein theconverter circuitry includes a charge removing circuit connected to thepiezoelectric transducer.
 34. The system of claim 20, wherein theconverter circuitry includes a charge reclaiming circuit connected tothe piezoelectric transducer and the one or more charge holdingelements.
 35. The system of claim 20, wherein the converter circuitry isconfigured such that capacitances of the piezoelectric transducer andthe one or more charge holding elements determine how much charge isreclaimed.
 36. The system of claim 20, wherein the converter circuitryis configured to implement a multi-stage process utilizing the one ormore charge holding elements.
 37. A pump comprising: a pump bodyconfigured to at least partially define a pumping chamber; apiezoelectric element responsive to a drive signal for pumping fluid inthe pumping chamber; and a pump driver configured to provide the drivesignal, the pump driver including a flyback boost circuit configured todevelop an accumulated charge associated with the piezoelectric elementand also a charge on one or more charge holding elements, a chargescavenging circuit configured to provide a charge scavenged from thepiezoelectric element to the one or more charge holding elements, acharge removing circuit configured to substantially remove or dischargea remaining charge from the piezoelectric element, and a chargereclaiming circuit configured to apply the scavenged charge to thepiezoelectric element with an opposite polarity in relation to thepolarity of the remaining charge.
 38. The pump of claim 37, wherein thepump driver is configured to provide the drive signal responsive tovoltage pulses.
 39. The pump of claim 38, further comprising: acontroller configured to generate the voltage pulses.
 40. The pump ofclaim 37, wherein the one or more charge holding elements include acapacitor or a second piezoelectric element.
 41. The pump of claim 37,wherein the flyback boost circuit includes an inductor array configuredsuch that different portions of the array are utilized for transferringcharge to the piezoelectric element and a capacitor, respectively. 42.The pump of claim 37, wherein the flyback boost circuit includes aninductor array configured such that different portions of the array areutilized for transferring charge to first and second piezoelectricelements, respectively.
 43. The pump of claim 37, wherein the pumpdriver is configured such that capacitances of the piezoelectric elementand the one or more charge holding elements determine how much charge isreclaimed.
 44. The pump of claim 37, wherein the converter circuitry isconfigured to implement a multi-stage process utilizing the one or morecharge holding elements.